Liquid chromatography is a process by which a substance may be separated into its constituent ions or molecules. Typically, the substance is dissolved in a solvent and is driven through an analytical column by a pump. The analytical column is filled with a packing material known as a “stationary phase.” The various components of the solution pass through the stationary phase at different rates, due to their interaction with the stationary phase.
Liquid chromatography may be used as an initial phase prior to further analysis via a mass spectrometer. Per such an arrangement, a substance to be analyzed is first separated into its constituents by a liquid chromatograph. Thereafter, time-sequenced samples are delivered from the output of the liquid chromatograph to the input of the mass spectrometer, i.e., into the ion source of the mass spectrometer.
In instances in which the mass spectrometer utilizes electrospray ionization, it is known to embody the liquid chromatograph as a small polymeric chip. In other words, the analytical column exists as a channel (packed with a treated stationary phase material) extending through the body of the chip. The output of the packed channel is connected to a second channel that extends to distal region of the chip, which is fashioned as a spray tip. The spray tip portion of the chip is inserted into the ion source of the mass spectrometer. Thus, the substance to be analyzed is separated into its constituents by the packed column embodied on the chip, and is then delivered, via the spray tip, into the mass spectrometer for further analysis.
The above-described scheme exhibits certain characteristics. To properly interface the chromatography chip with the ion source of the mass spectrometer, the spray tip region of the chip must be precisely shaped to mate with the ion source. Additionally, the chip must be precisely oriented relative to the mass spectrometer. Thus, the chromatography chip must be designed in light of the specific mass spectrometer to which it is to be mated, meaning that it cannot effectively function as a stand-alone unit.